Cross-connection Control for Wastewater Treatment Plants
Department of Health Mission We work with others to protect and improve the health of all people in Washington State. 2
Presentation Overview • Descriptions • Requirements • The Project • Common Deficiencies
Descriptions 4
Wastewater Treatment Plants • Many of the wastewater treatment and collection facilities are now old and worn, and require improvement, repair or replacement to maintain their useful life. • The character and quantity of contaminants presenting problems today are far more complex than those that presented challenges in the past. 5
Wastewater Plant Schematic
RAS/WAS Pumps Digesters Secondary Clarifier Solids Handling Primary Clarifier Aeration Basin Head works
Backflow Incidents • Hundreds of incidents documented – USC CCC Manual (2009) – EPA’s CCC Issue Paper ( 2002) – PNWS-AWWA Incident Manual (1995) • Incident impacts – Health – Costs of investigation and clean-up – Litigation • Incidents are under-reported – Not detected or not reported 9
Reported WA Backflow Incidents Cause and Number Number of Reports (1996-2017) 74 Caused by backpressure 51 Caused by backsiphonage 18 Unknown cause 5 • Corpus Christi and Chicago 10
BACKFLOW AT A WASTEWATER TREATMENT PLANT • In December 1983, effluent from a wastewater treatment plant in San Antonio, Texas, backflowed into the potable water system at the plant because of maintenance activities. • Eight employees reportedly suffered gastrointestinal problems. Fortunately, a reduced- pressure principle backflow-prevention assembly was in place at the water service connection to the plant. This assembly contained contamination within the plant site.
Requirements 12
CCC at Sewage Facilities Cross-connection control (CCC) at sewage facilities has two functions: • Protecting the public potable water system from contamination • Protecting the onsite domestic potable water system from contamination.
Basis Three concepts form the basis for cross-connection control at sewage facilities. • The public water supply is protected by premise isolation RPBAs and RPDAs and in-plant air gaps. • On-site domestic potable water is protected by RPBAs and in-plant air gaps. • Actual or potential connections to sewage, process water or toxic chemicals are downstream of an air gap.
Potable Water • Do not use potable water for purposes other than drinking, personal hygiene and emergency washing facilities. • Laboratory usage is permissible provided that the laboratory supply line is fitted with an RPBA and, where appropriate, there are in-lab air gaps.
“Ideal” Situation
Complicated Situation
The Orange Book • Must locate air gaps, RPBAs and RPDAs above ground level • Must locate premise isolation backflow preventer adjacent to meter or property line • Supply all hose bibs, wall hydrants, and yard hydrants, whether above or below ground, interior or exterior, through an air gap
The Orange Book “Facility designs must include a pressurized water system supplied through an air gap to facilitate cleaning or flushing of wet wells, dry wells, tanks, basins and equipment.”
Reclaimed water • Must protect potable water from reclaimed water as if reclaimed water were sewage • Reclaimed water is protected as if reclaimed water were potable water
Potable Water • Recommended that designers locate all potable water piping at ground level or above to prevent future inadvertent cross connection. • Do not route city water/potable water piping through wet well areas to prevent future inadvertent cross-connection.
Emergency Washing • Designers should try not to locate emergency washing facilities(eye wash stations/showers) below ground level. • If designers cannot avoid locating emergency wash stations below-ground must demonstrate that the installation will protect potable water supplies from accidental contamination.
Irrigation • Irrigations systems may use non-potable water taken downstream of a backflow preventer, disinfected plant effluent, reclaimed water or stormwater collected within the facility’s perimeter. • Ecology discourages use of potable water for irrigation; such use must include an RPBA.
Fire Protection The water supply to any fire protection system must be equipped with an RPBA located and installed in accordance with the requirements for the premise isolation backflow preventer.
Chemicals and Substances • Properly equipped water systems used with, connected to, or have the potential to come into contact with hazardous chemicals and substances • Proper equipment includes supplementary air gaps and backflow prevention devices appropriate to the degree of hazard that would result if those chemicals were to backflow into the facility piping systems
Odor Control • Odor control involves sewage aerosols and particulates. Water supplied to odor control equipment or to hose bibs in the odor control area is considered to be in direct contact with sewage. • Water supplied to odor control areas and equipment must utilize an air gap.
WAC 246-290-490 (4)(b) (ii) For service connections to premises posing a severe health cross-connection hazard including wastewater treatment plants, radioactive material processing plants, and nuclear reactors, the purveyor shall ensure that either an: (A) Approved air gap is installed for premises isolation; or (B) Approved RPBA or RPDA is installed for premises isolation in combination with an in- plant approved air gap.
Project 29
Background • Since 2007, ODW has collected cross-connection control data from the largest community water systems on the status of backflow prevention at wastewater treatment plants. • Water systems self-report their CCC data and ODW has not independently verified the information reported
Project Goals • Perform CCC hazard surveys of 47 severe health hazard facilities • Evaluate self-reported data for the associated PWS • Report findings to ODW, PWS, and the facility surveyed • Compile data to determine: – Program effectiveness. – Guidance, training, and resources needed. – Compliance with regulations.
Process • Contact the public water system CCS and discuss project. • Contact WWTP operator with PWS CCS to discuss the project. • Gather as much information as available to review before the survey. • Perform survey of the facility. • Write survey report. • Send report to all parties.
Findings Deficiencies Total found in Number of % Of Plants all plants plants Improper air gaps (majority of problem was 14 12 41% not enough distance between outlet and flood rim) No RPBA prior to air gap 8 5 17% Moving RPBA for hydrant tested annually 3 3 10% Improper protection for Chemical Injection 4 3 10% RPBA's installed below ground 31 18 62% Access restricted 0 0 0% Potential spoolpiece connection 2 2 7% Improper protection for Pump seal water 4 4 17% Valves installed downstream of AVB 5 4 14%
Findings Deficiencies Total found in Number of plants % Of Plants all plants No hosebib vacuum breaker 14 8 28% No RPBA for laboratory 12 9 31% Double check on hydrant construction 1 1 3% Non potable pipe before fire sprinkler 1 1 3% Complicated piping 1 1 3% Processed water to eye station 1 1 3% Washdown water not air gapped 4 4 14% Premise Isolation not at property line 2 2 7% Reclaimedan potable supplied to restroom 1 1 3%
Data • 29 surveys have been performed • 72 percent of facilities did not meet the regulations • All facilities were up to date on their backflow assembly testing • 88 percent of water systems coordinate with their authority having jurisdiction • 84 percent of systems have a Quality Control/Quality Assurance Program
Common Deficiencies 36
Spool Piece
RPBA Not at Property Line
Direct Connection to Sewer Line
Improper Assembly
Improper Assembly
Proper Air Gap
Air Gap Below Flood Rim
Improper Air Gap
Air Gap Below Ground
Air Gap Defeated
No Hose Bib Vacuum Breaker
No Hose Bib Vacuum Breaker
RPBA Located Below Ground
Improper Protection for Chemical Injection
Proper Labeling
Improper Labeling
Pump Seal Water
Pump Seal Water
Eye Wash Stations
Corroded Assembly
Odor Control Station
Auxiliary Water Supply
Access To Assemblies
Mystery Assembly
Unable to Maintain
Direct Cross Connections
Autoclave
Shut Off Valve Moved
Shut Off Valves Removed
Bypass
Valve Downstream of AVB
No HBVB
Old Service Line
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